The usability of a system has been highly estimated which, when receiving a sentence written in a natural language, interprets the sentence, collects information relevant to the input sentence from knowledge sources composed of data written in the natural language, interprets the collected pieces of information, processes the pieces of information, for example, by combining some pieces of information, and proposes the processed pieces of information. An example of such a system as has lately attracted the highest attention is a question-answering system.
For example, Patent Literature 1 discloses a method in which a question-answering system is built up by determining a lexical answer type (LAT), executing a search, and analyzing the search result using the LAT.